(FOX 11 / AP) - A search for a computer hard drive and anything else linked to the husband-and-wife shooters who killed 14 in the California attacks stretched into the weekend, as specialized divers with the FBI looked through a San Bernardino lake for abandoned evidence.

Investigators have said the killers tried to cover their tracks by destroying emails, cellphones and other items at their home in Redlands. They were tipped that the small lake in a park about 3 miles from where the shootings happened might hold the hard drive, according to a law enforcement official briefed on the investigation but not authorized to speak publicly about the case.

On Saturday, they searched the lake for a third day while funerals continued for those who were the slain. The search began Thursday after authorities learned the shooters, Syed Rizwan Farook, 28, and Tashfeen Malik, 29, may have been in the area the day of the attack, said David Bowdich, chief of the FBI's Los Angeles office. He said the search could last several days.

Farook, a U.S. citizen, and his Pakistani-born wife, opened fire Dec. 2 at a holiday luncheon attended by many of Farook's co-workers in the San Bernardino health department. The couple died in a shootout with law enforcement hours later, leaving behind a 6-month-old daughter.

Authorities say Farook and Malik, who came to the U.S. on a fiancee visa in July 2014 and married her husband the next month, were not known to law enforcement before the shootings. But since the attack they have determined the couple discussed martyrdom and jihad online as early as 2013.

Farook's longtime friend and relative-through-marriage, Enrique Marquez, bought the assault rifles used in the shooting more than three years ago, about the time he converted to Islam, according to the law enforcement official. Farook asked Marquez to buy the rifles because he was worried he wouldn't pass the background check himself.

Marquez, who checked himself into a mental hospital after the attack, told investigators that he and Farook were plotting an attack in 2012.

Idaho Sen. Jim Risch, a Republican who sits on the Senate Select Committee on Intelligence, said they had an actual plan, including buying weapons, but became apprehensive and shelved it because of law enforcement activity and arrests in the area.

Marquez hasn't been charged with a crime and has been cooperating with authorities.